It seems Ubuntu is confused by the use of 7001 for the port. It does
appear in the 'reserved' ports lists as 'afs3-callback'
Changing this to another unreserved value, 47001 for example, and its
fine. I guess windows is more sloppy on this front.
Thanks for the advice, Marcin. Wireshark looks interesting too, I just
have to learn how to comprehend all the output now!
Marcin Kasperski wrote:
>> When I run System>Network Tools>Portscan on localhost, I can see port
>> 7001 is open with a service called 'afs3-callback'.
>>>> This is somewhat misleading and does not matter anything. Simply, you
> have in your /etc/services the info that port 7001 is typically used
> by afs3-callback (whatever it is). Similarly the same program will
> say that you are using service 'www' if port 80 is open. This is
> just popular convention applied by many programs - instead of showing
> numerical port, show text assigned to this port in /etc/services.
>> To truly check what is running on given port, try sth like
>> sudo netstat -l --tcp -p
>> (there surely is some GUI which does the same, but I am not expert in
> GUIs, learned command lines before they existed ;-))
>> You will get the list of all processess listening on TCP ports. In
> particular you may see lines like
>> tcp 0 0 *:4433 *:* LISTEN 26164/apache
>> (this is from my host, on port 4433 there is some apache process
> runing, pid of the process is 26164). To check in more detail what
> process do you see, try sth like
>> ps 26164
>> (giving the pid from the line above) and you will see the command
> which spawned the process. Of course you can also search for this
> pid in some GUI process monitor.
>>> Some alternative way to check some ports is to ... telnet there.
> For example
>> telnet localhost 7001
>> You get direct connection to the other side. It may give you some info
> (many daemons send some initial string), or ... not. But in particular
> it will tell you whether there is any process on the other side (if
> not, you get 'Connection refused' error). To leave such session press
> Ctrl-] and enter 'quit' after 'telnet>' prompt.
>>>> The odd thing is, once I have run the Portscan, my client suddenly
>> sees the server and connects!
>> (...)
>>>> Why does Portscan seem to open the port for me?
>>>> The only reasonable guess I can make is that your server misbehaves
> somehow, for example incorrectly handles some initial connection(s).
> Portscan opens connection to it and closes it, maybe it helps your
> server.
>> Another guess is that maybe you just missed something. For example,
> maybe your server works when accessed as localhost but does not work
> when accesssed on yourmachinetrueinterface (or reverse)...
>> If you need to diagnose your network communication in more detail,
> you may take a look at wireshark (formerly ethereal) package,
> it lets you capture and review the whole network communication.
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